A review on the compressive strength of concrete improved with various types of pozzolan Praveen Regunathan Civil Engineering Department, College of Engineering, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, 43000 Kajang, Selangor, Malaysia. Email: r.praveenl@yahoo.com Leong Sing Wong College of Graduate Studies, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, 43000 Kajang, Selangor Malaysia. Email: wongls@uniten.edu.my Noraisyah Nordin Civil Engineering Department, College of Engineering, Universiti Tenaga Nasional, Jalan IKRAM-UNITEN, 43000 Kajang, Selangor, Malaysia. Email: nnoraisyah@gmail.com Cement is still the dominant binder supply for concrete industry. The most important environment and health issues facing the cement industry are greenhouse gas emissions and atmospheric releases, primarily of carbon dioxide. Cement production is highly energy intensive process involving significant environmental damage with respect to carbon dioxide production. This review paper presents the usage of pozzolan such silica fume, metakaolin and fly ash as a supplementary cementation material that induces sustainability to concrete by reducing the carbon dioxide emission of cement production. In additional, review is also done on the effectiveness of metakaolin, silica fume and fly ash on the compressive strength related to durability of high performance concretes. Keywords cement, concrete, silica fume (SF), metakaolin(mk), fly ash I. Introduction Concrete is the world's most utilized material for infrastructural development in both the developing and developed countries. Although the points of interest in cement as a development material, the creation of cement takes on at an incredible expense to the globe, environmental damage with respect to CO 2 production and raw material acquisition [1]. Hence, in the perspective of sustainability and ecological connected with the making of cement, the utilization of pozzolan to partially replace Portland cement is a wise option in the making of green concrete. Pozzolanic added substances are the materials that can improve concrete properties such as strength, durability and impermeability [2]. Furthermore, concrete with high compressive strength has progressively been utilized as a part of structural building work since it has influence in decreasing the sizes of columns and beams [3]. Concrete with twenty eight curing days will have compressive strength higher than 41 MPa that can be considered as high strength concrete [4]. In general, to achieve high compressive strength concrete, supplementary cementing materials such as silica fume, fly ash or natural pozzolan as metakaolin can be utilized in order to create extra strength by pozzolanic reaction. High strength concretes were found with the usage of silica fume and natural pozzolan as concrete supplementary materials, and it was discovered that the mix of the two can be utilized as a part of delivering high quality concrete in the scope of 69 MPa to 85 MPa at 28 days with moderate workability [5]. Silica fume is a residue resulting from the making of ferrosilicon and silicon metal. It has a high content of silicon dioxide (SiO 2 ) consists of very small spherical particles. In view of this, it has been a widespread mineral admixture to be used in high strength concrete [6]. In any case, silica fume is expensive compare with Portland concrete type I or fly ash. The burning of anthracite or bituminous coal in thermal power plant produces fly ash and it has been uses for cement replacement in matter of improving compression strength on concretes [7]. In addition, using metakaolin as partial replacement for cement has been improved the performance of the concrete said by Sabir BB [8]. Metakaolin is unique in relation to common pozzolan or different sorts of artificial pozzolan in such a path, to the point that it obliges a train of procedures to get pozzolan property. It is a thermally activated aluminasilicate material obtained by calcining kaolin clay within the temperature range 650 800 C [8]. This paper reviews the compressive strength of concrete improved using various types of pozzolan with emphasis on the strength of concrete having pozzolan as a partial cement replacement. There are three types of pozzolan chosen for this study which are silica fume, fly ash and metakaolin. The test procedure and results of compressive strength for the silica fume and metakaolin improved concrete were reviewed from the research works of Erhan Guneyisi et al, [9] and for the fly ash by P. Nath P and Sarker, [10]. 240
2.1 Material II. Experimental details The materials used were Portland cement, metakaolin (MK), silica fume (SF), fly ash fine and coarse aggregates. Based on the study of Erhan Guneyisi [9] with reference to the standard of Portland cement (CEM I42.5R) conforming to the Turkish standard TS EN 197 1 (which mainly based on the European EN 197 1), grade MK and SF were utilized as cementations materials. P. Nath and P. Sarker, [10] utilized the Portland cement conforming to Standards Australia (AS 3972). III. Mixture proportions and casting of concrete Concretes were prepared in accordance with standard method in a power driven revolving pan mixers and comprising of a control mixture. Aggregate mixtures to cast concrete were kept at constant properties for all samples. Table 1 shows the type, mixing proportion and the size of concrete from various research works. According to Erhan Guneyisi [9], mixtures of water ratios 0.25 and 0.35 were selected for sample preparation. Metakaolin and silica fume were partially replaced to Portland cement with 5% and 15% mineral admixture for both water cement ratios. For the compression test, 150 150 150 m cubes size was used as a standard specimen. In another mix design, water to cement ratio for concrete mixture was 0.29 and the Portland cement was partially replaced with fly ash by 30% and 40% according to the weight Portland cement. Additionally, concrete cylinders with 100 mm diameter and 200 mm height were casted for compression test as reported by P. Nath and P. Sarker, [10]. IV. Compressive strength of concrete with pozzolan as partial replacment of cement On the basis of the study of Erhan Guneyisi [9], the data concerning the compressive strength development with water to cement ratio and curing period for the concretes incorporating silica fume (SF) and metakaolin (MK) are presented in Fig. 1. The effect of MK and SF on compressive strength of concrete can clearly be observed from the figure. The SF and MK concretes had consistently higher compressive strength than those of the control concretes. The 28-days compressive strength of the concrete with water to cement ratios of 0.25 and 0.35 were ranged between 75.4 85.8 MPa and 61.8 73.3 MPa, respectively, independent of the type of the mineral admixture and replacement level. The figure indicated that there was a systematic increase in compressive strength with the increase in MK and SF content for both of the concrete groups. This is more pronounced for concrete with water to cement ratio of 0.35. For example, at 28 days curing duration, the compressive strength gains of 35%, 43%, 59%, 39%, and 44% for plain, SF5, SF15, MK5, and MK15 concretes with water to cement ratio of 0.35, respectively, with reference to 3 curing days compressive strength were significantly observed. On the other hand, 13%, 27%, 39%, 18%, and 29% compressive strength gains were observed for the concrete group with water to cement ratio of 0.25. In both cases, SF incorporated concrete exhibited higher rate of strength gain than plain and MK concretes. Poon et al. [11] investigated the mechanical properties of the metakaolin and silica fume concretes. Regarding the use of MK, they demonstrated that MK concrete had relatively higher strength development than that of control concrete. It was reported that the ratio of the 90 curing days compressive strength to the 28 curing days compressive strength for the MK concrete was found to be 1.18, which is primarily dependent on the partial replacement of MK and water to cement ratio. For water to cement ratio of 0.35, the concrete with MK had higher compressive strength than the plain and SF concretes. However, the compressive strength development of MK and SF concretes produced by 0.25 water to cement ratios shows almost similar trend. The addition of metakaolin into the concrete matrix improved the bond between the cement paste and aggregate particles as well as increasing the density of the cement paste which in turn significantly enhanced the compressive strength of the concrete. The main factors that affect the contribution of metakaolin in the compressive strength are the filling effect, the dilution effect, and the pozzolanic reaction of metakaolin with CH [12]. Research from Wild et al. [13] found that inclusion of silica fume in concrete mixture, greatly affected short-term strength gain of concrete. The difference in strength development in ordinary Portland cement concrete and silica fume concrete can be attributed to the rapid formation of an inhibiting layer of the reaction products preventing further reaction of SF with calcium hydroxide. Compression test results on concrete from the study of P. Nath and P. Sarker, [10] are shown in Fig. 2. The results indicate that incorporation of fly ash in concrete decreased strength at the earlier age as compared to that of the control concrete. Concretes with 30% fly ash (B30) have shown higher strength gain than those with 40% fly ash (B40). The strength of fly ash concretes developed at a higher rate than that of control concrete (B00) until 56 curing days. The strength increase after 56 days of curing age is very small in all the mix designs of concrete. However, fly ash concretes achieved over 80% of control concrete s strength at 28 curing days. They reached 92% and 96% of control concrete compressive strength at 56 curing days, for 40% and 30% fly ash content respectively. 241
Fig.1. Effect of silica fume and metakaolin on compressive strength development of concretes [9] Fig.2. Effect of Fly ash on compressive strength development of concretes [10] 242
Table 1: Type, mix portion and size of the concrete from the various research work Research work Type of concrete Mixing Proportion Concrete size Erhan Guneyisi, [9] Control concrete W/c ratio: 0.25 and 0.35 Portland cement : 100%, Concrete with metakaolin,mk W/c ratio :0.25 and 0.35 Metakaolin : 5% (MK5) and 15% (MK15) Portland cement 95% and 85% Concrete with Silica fume, SF W/c ratio :0.25 and 0.35 Silica fume : 5% (SF5) and 15% (SF15) Portland cement : 95% and 85% P. Nath and P. Sarker, [10] Control Concrete W/c ratio : 0.29 Portland cement:100% (B00) 100 200-mm cylinder Concrete with Fly ash W/c ratio: 0.29 Portland cement: 70% and 60% Fly ash: 30% (B30) and 40% (B40) 100 200-mm cylinder V. CONCLUSION Based on the review on the compressive strength improvement with various types of pozzolan in concrete as presented above, the following conclusions can be drawn: 1. SF and MK concrete have absolutely higher compressive strength than the control conrete over long term curing duration. There was an efficient increment in compressive quality with the increment in MK and SF content for both water to cement of the stated water to cement ratios. The rates of compressive strength advancements of MK and SF improved concrete were higher than that of control concrete for both water to cement ratios. These pozzolans were proven to be capable to improve the strength of concrete. 2. The 28-days of curing strength dropped when cement was partially replaced with fly ash in concrete. The compressive strength reached more than 80 MPa at 56 curing days. Strength development of the fly ash concretes continued to increase noticeably up to 56 days of curing. Acknowledgment The authors would to acknowledge the funding from the Ministry of Education of Malaysia through Exploratory Research grant scheme (Project Grant number: 13012013 ERGS) References [1] Chengzhi Z., Aiqin W., Mingshu T. and Xiaoyu L, Cement and Concrete Research, 1996, 26(6), 943-947. [2] F.M. Lea, The Chemistry of Cement and Concrete, 3rd ed., Edward Arnold, London, 1974. [3] Chai Jaturapitakkul, Kraiwood Kiattikomol, Vanchai Sata, Theerarach Leekeeratikul, Use of ground coarse fly ash as a replacement of condensed silica fume in producing high-strength concrete, 2003. [4] ACI Committee 363, State of the art report on high-strength concrete, ACI 363R-92, ACI Manual of Concrete Practice: Part I, American Concrete Institute, Detroit, 2000. [5] M.J. Shannag, High strength concrete containing natural pozzolan and silica fume, Cem. Concr. Compos. 22 (2000) 399 406. [6] Alexander MG, Magee BJ. Durability performance of concrete containing condensed silica fume. Cem Concr Res 1999;29:917 22. [7] ACI Committee 232. Use of fly ash in concrete (ACI 232.2R-03). American Concrete Institute: Farmington Hills, MI; 2003. p. 41. 243
[8] Sabir BB, Wild S, Bai J. Metakaolin and calcined clays as pozzolans for concrete: a review. Cem Concr Compos 2001;23:441 54. [9] Erhan Güneyisi, Mehmet Gesoglu, Seda Karaoglu, Kasım Mermerdas, Strength, permeability and shrinkage cracking of silica fume and metakaolin concretes 2012. [10] P.Nath, P.Sarker, Effect of Fly Ash on the Durability Properties of High Strength Concrete,2011. [11] Poon CS, Kou SC, Lam L. Compressive strength, chloride diffusivity and pore structure of high performance metakaolin and silica fume concrete. Constr Build Mater 2006;20:858 65. [12] Wild S, Khatip JM, Jones A. Relative strength, pozzolanic activity and cement hydration in superplasticized metakaolin concrete. CemConcr Res 1996;26:1537 44. [13] Wild S, Sabir BB, Khatib JM. Factors influencing strength development of concrete containing silica fume. Cem Concr Res 1995;25:1567 80. [14] Ding JT, Li Z. Effects of metakaolin and silica fume on properties of concrete. ACI Mater J 2002;99:393 8 [15] Neville AM. Properties of concrete. 4th and final ed. England: Addison Wesley Logman; 1996 [16] Poon C, Lam L, Kou SC, Wong Y, Wong R. Rate of pozzolanic reaction of metakaolin in high-performance cement pastes. Cem Concr Res 2001;31:1301 6. [17] Güneyisi E, Gesog lu M, Mermerdas K. Improving strength, drying shrinkage, and pore structure of concrete using metakaolin. Mater Struct 2008;41:937 49 [18] Cao HT, Bucea L, Meek E, and Yozghatlian S, Formulation and Durability of Fly Ash Blended Cement,1996. [19] Chindaprasirt P, Homwuttiwong S, Sirivivatnanon V, Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar,2004. [20] Camoes A, Aguiar B, and Jalali S, Durability of low cost high performance fly ash concrete,2003 244